Creating decorative quilts by hand has become a popular avocation. A typical quilt is comprised of at least two fabric layers which are stacked and stitched together. Generally the quilt is comprised of a “top” layer, a “bottom” or “backing” layer, and an intermediate “batting” layer. The top layer is typically decorative and is produced as a consequence of the creative and artistic effort of the quilt maker. The backing layer is usually simple and aesthetically compatible with the top. The batting layer generally provides bulk and insulation. The specific process of sewing the sandwich of the three planar layers together is generally referred to as “quilting”. The quilting process usually consists of forming long continuous patterns of stitches which extend through and secure the top, backing, and batting layers together. Oftentimes stitch patterns are selected which have a decorative quality to enhance the overall aesthetics. A general goal of the quilting process is to produce precise consistent stitches that are closely and uniformly spaced.
Quilting traditionally has been performed by hand without the aid of a sewing machine. However, hand quilting is a labor-intensive process which can require many months of effort by a practiced person to create a single quilt. Accordingly, it appears that a trend is developing toward using machines to assist in the quilting process to allow most of the quilter's effort to be directed toward the creative and artistic aspects of the top layer.
Machine quilting can be performed in a variety of ways. For example, a user can operate a substantially conventional sewing machine in a “free motion” mode by removing or disabling the machine's feed dogs. This allows the user to manually move the stacked quilt layers relative to the machine's needle, either directly or via a quilt frame, to produce desired patterns of stitches. In practice, the sewing machine is run at a relatively constant speed as the user moves the stacked quilt materials under the needle. This process typically requires significant operator skill acquired after much practice to enable the operator to move the quilt stack in synchronism with the needle stroke to form high quality stitch patterns. Thus, free motion quilting with a conventional sewing machine requires significant user skill and yet frequently yields imperfect results, particularly when forming curved and intricate stitch patterns.
Machine quilting can also be performed by using a wide range of specialized hand guided quilting systems which have become available in recent years. The characteristics and features of such systems are discussed in an article which appeared in Quilter's Newsletter Magazine (QNM), April 2003, by Carol A. Thelen. The article identifies three categories of such systems; i.e., (1) Table top set-ups, (2) Shortarm systems, and (3) Longarm systems. They are generally characterized by a table which supports a frame and a quilting/sewing machine. The frame includes rollers which hold the quilt layers so as to enable a portion of the layered stack to be exposed for stitching while the remaining layer portions are stored on the rollers. The quilting/sewing machine rests on a carriage mounted for movement (e.g., along tracks) relative to the frame and table. The carriage is generally provided with handles enabling an operator to move the machine over the surface of the quilt. The QNM article further discusses optional add-ons and accessories enabling various electronic functions, including stitch regulation, to be added to basic shortarm or longarm systems.
Applicant's U.S. Pat. No. 6,883,446 describes an apparatus which permits a user to manually move a stack of fabric layers across a planar bed, or plate, beneath an actuatable stitch head. The apparatus includes a detector for detecting the movement of the stack for the purpose of synchronizing the delivery of stitch strokes to the stack movement. This approach enables the insertion of uniform length stitches while allowing the user to move the stack within a wide range of speeds, to start or stop the stack movement at will, and to guide the stack in any direction across the planar bed.
The preferred embodiments described in applicant's U.S. Pat. No. 6,883,446 employ a detector configured to detect stack movement within the throat space of a quilting/sewing machine by measuring the movement of at least one surface of the stack as it moves across the planar bed. As described, a preferred detector responds to energy, e.g., light, reflected from a target area on the stack surface (top and/or bottom) within the machine's throat space. The detector preferably provides output pulses representative of incremental translational movement of the stack along perpendicular X and Y directions. The output pulses are processed to determine the distance the stack moves. When the cumulative stack movement exceeds a threshold magnitude, a “stitch stroke” command is issued to cause the stitch head to insert a stitch through the stacked layers. As the user moves the stack across the planar bed, additional stitch stroke commands are successively issued to produce successive stitches.
Applicant's U.S. Pat. No. 6,883,446 primarily contemplates that the user directly grasp, or touch, the stacked fabric layers to push and/or pull the stack across the planar bed. However, the application also recognizes that the user could, alternatively, mount the stack on a conventional quilt frame and then grasp the frame to move the stack across the planar bed to enable the detector to sense stack surface movement.